Process for the treatment of lumber



June 30, 1959 H. M. HUTcHlNsoN 2,892,261

PRocEss FOR THE TREATMENT oF LUMBER Filed July 1, 1955 2 Sheets-Sheet lBY TM@ June 30, 1959 H. M. HurcHlNsoN v 2,892,251

PROCESS F 0R THE TREATMENT OF LUMBER Filed July 1, 1955 2 Sheets-Shree?.2

#pM/70N M. Marcy/fvwm INVENTOR.

United States Patent O PROCESS FOR THE TREATMENT F LUMBER Hamilton M.Hutchinson, Eugene, (lreg. y Application July 1, 1955, Serial No.`519,506

12 Claims. (Cl. S14- 9.5)

This invention relates to the treatment of Wood and wood products, andhas particular reference to a process for drying and preserving lumber.

One of the principal objects of this invention is to provide a novelprocess for treating green lumber to dry the same.

Another object of this invention is to provide a novel process fordrying lumber in substantially shorter periods of time than haveheretofore been possible.

. Another object of this invention is to provide a novel process forsimultaneously drying lumber and rendering the same water-resistant. Y

Yet another object of this invention is to provide a novel process fordrying lumber which results in a product having physical propertiessuperior to those of lumber dried by prior art methods. .v

A further object of this invention is to provide a drying process forthe treatment of lumber and to simultaneously render the sameWater-resistant, flame-resistant and resistant to pests such as termitesand the like.

Other objects and advantages of this invention it is believed will bereadily apparent from the following detailed description of a preferredembodiment thereof, when read in connection with the accompanyingdrawings.

In the drawings:

Figure 1 is a diagrammatic view illustrating an apparatus for carryingout the process of this invention.

Figure 2 is a diagrammatic side elevation, partly in section, of atreating tank utilized in carrying out the process of this invention. 1

Figure 3 is a sectional elevation taken substantially on the line 3-3 ofFigure 2.

Figure 4 is a sectional elevation taken substantially on Ithe line 4-4of Figure 2.

1 In carrying out the process of this invention, the green lumber isfirst placed in a conventional sticking rack so that a plurality ofvertical, spaced rows of the lumber are formed. Preferably, the boardsare placed horizontally, but on their edges so as to present the maximumAareas thereof4 in a vertical position. Additionally, it is preferred totie or strap the lumber to the rack in such manner that it isconveniently handled by conventional fork lift mechanisms.

After stacking the lumber, it is preferably treated with live steam.Although not essential, this steam treatment performs three importantfunctions: it cleans the lumber free of sawdust and other foreign'matter; it raises the,

jected to the action of a liquid drying medium for a' length of time andat a temperature sufficient to drive 0E from the lumber the desiredamount of water. have 2,892,261 Patented June 30, 1959 ICC discoveredthat lumber may be dried quickly and evenly by treating the same with aWater-immiscible liquid treating medium having a iinal boiling pointhigher than the boiling point of water. Many such liquid treating mediamay be used, such as, for example, carbon tetrachloride, variousrelatively high-boiling petroleum hydrocarbon fractions, etc. In thecase of such hydrocarbon fractions, it is preferred to select thosewhich do not contain appreciable amounts of heavy ends, i.e., componentsboiling above about 700 F., since such heavy ends tend to deposit on thewood itself and require excessively high treating temperatures forremoval thereof. I have found that so-called naphthas or petroleumsolvents, and particularly commercial aliphatic (high aniline type)solvents, such as for example, Standard Oil Thinner #410 (boiling range360-450 F.) are especially suitable.

T he application of the liquid treating medium is preferably carried outin an enclosed tank through which the liquid treating medium may becirculated, for removal of water from and for reheating of the liquid atpoints exteriorly of the tank. Optimum drying times are obtained byiirst placing the lumber into the tank and then introducing the heatedliquid either by spraying the same over the lumber or by ooding thelumber therewith, or both.

I have found that temperatures above 212 F. must be employed in order toobtain quick and proper drying of the lumber. That is, the temperatureof the treating medium at and after the time of initial contact with thewood should be above 212 F. so that the moisture is continuously drivenout of the wood, thus preventing ap'- preciable absorption of thetreating medium itself. While the specific treating temperature willvary, depending upon thetype of lumber, the specific treating mediumernployed, and other process variables, it has been found' that atemperature range of between about 250 and about 450 F. is satisfactoryfor most operations. The drying time is one of the process variablesupon which the temperature is dependent, but generally from about 4 toabout 12 hours is sufficient. It will be understood that, assumingconstant temperature, the drying time primarily depends upon the initialWater content, size of the charge of lumber and the sizes of theindividual pieces thereof.

During the drying operation, Water is continuously re-V movedfrom thelumber in the form of vapor, and to some extent it is entrained in thecirculating treating medium. of water-resistance may be obtained byintroducing into I have found that a superior product from thestandpoint of water-resistance may be obtained by introducing into thetreating medium a minor proportion of a high melting point (i.e., aboveabout F.) Wax such as paraffin wax, a microcrystalline wax, beeswax,etc. Other treating chemicals such as insecticides, dyes, etc., may beadded to the treating medium for application to the Wood during thedrying operation, if desired.

After the desired drying period has passed, the treat-l ing medium iswithdrawn from the tank and the lumber,

steamed free of vapor, or if desired, the lumber may be removed from thetank and the treating medium left to remain in the tank for a suicientlength oftime toV permit it to lose an appreciable quantity of its heatbefore removal, rather thanto immediately expose the hot A lumber to therelatively cool ambient air with .theat'g'v tendant danger of checking,cracking, warping or socalled case-harding of the wood.

Referring now to the drawings, `a specific example of the process ofthis invention will now be described, as carried out in the apparatusshown therein. This apparatus includes a pair of identical treatmenttanks and 11, substantial portions thereof being sunk below the surfaceof the ground, as shown in Figure 2, in order to facilitate loading andunloading of the tanks. By utilizing a pair of tanks, the process can begreatly speeded up, one of the tanks being loaded or unloaded while theother tank is being used in treating the lumber.

The tanks 10 and 11 are each `generally rectangular in shape, each ofthe open tops thereof being provided with a cover member 12, 13. Bracketmembers 14, are provided adjacent each corner of the respective ycovermembers 12 and 13 for removal thereof by means of a lifting assembly 16,as shown in Figure 3. inasmuch as the two tanks are identical, theremainder thereof will be described in connection with the tank 11. Thetank 11 is provided with -a channel element 20 extending about the outerperiphery thereof, the bottom edge 21 of the cover member 13 resting onthe channel element which is filled with water or other iluid 22 tofunction as a vapor seal.

The tank 11 is further provided with a pair of upper spray pipes 25connected together at one end with a transverse pipe 26, and a pair oflower spray pipes 27 connected together at one end with a transversepipe 29. Liquid inlet lines 30 lead to each of the transverse pipes 26in the two tanks 10 and 11, and liquid inlet lines 32 lead to each ofthe transverse pipes 29.

The remainder of the apparatus can best be described in connection withthe following description of a preferred embodiment of the presentinvention: A load of 2 x 6 x 24 ft. boards of rough green common Douglasr, containing roughly 50% moisture, was first struck, steamed asdescribed above for about 1/2 hour and then placed in the tank 11 andthe cover member 13 replaced thereon. The liquid treating medium(Standard Oil Thinner #410 containing 1% by weight of Barecro Wax,melting point 200 F., produced by Barnsdale Oil Co. of Tulsa, Okla.) waspumped by means of the pump 40 from the reservoir 41 through the heatexchanger 42 wherein, by exchange with steam from the boiler 43 throughline 44, the medium was heated to about 250 F. The heated treatingmedium was then pumped through the line 45. With the valve 46 open andthe valve 47 closed, the fluid fed through the inlet lines 30 and 32into the tank 11 and out through the apertures (not shown) in the spraypipes 25 and 29, forming the spray pattern shown in Figure 3. Inasmuchas the tank 10 was not then in use, the valves 46a and 47a were bothclosed. Thus the lumber was sprayed from all sides with the hot fluid,until the load of lumber was completely submerged in the treatingmedium, which was then continuously circulated through the tank for aperiod of Iabout six hours.

The fluid treating medium was circulated, and thus continuouslymaintained at a temperature of about 250 F., through the overflow line50, and through the connecting lines 51, 52 and 53 to the reservoir 41.A portion of the iluid proceeded through the valve 55 and line 56,through the condenser 56a and to the still 57 wherein water driven offfrom the wood was taken olf overhead through the line 58 and pumped, bymeans of the pump 59, through the steam boiler 43. The liquid treatingmedium comprised the bottoms from the still and was fed through the line60 to the reservoir.

After the six-hour treatment period, the valve 65 in the drainage line66 was opened and all of the uid was drained from the tank into thereservoir, the pump 40 having been previously shut down. Dry steam at250 F. was then blown through the lines 44, 68, valve 47 (how opened),and lines 30 and 32 into the tank to steam the wood for a period ofabout IAL hour, thereby driving off additional moisture. Following this,the valve 47 was closed, the valve 46 opened, and dry air blown from theblower 70 through the lines 30 and 32 into the tank for a period ofabout two hours, thus gradually reducing the temperature of the lumberand driving oi additional water vapor therefrom. During the steaming andblowing operation, the valves 55 and 65 were opened and the valve 71 wasclosed so that the water vapor was forced out through the lines 66 and50, thence through the condenser 56a and thence into the still 57 forseparation of residual treating medium.

The cover 13 was then removed and the load of lumber, which now had amoisture content of about 15%, was lifted out. The lumber so 'treatedwas fully equivalent to kiln-dried lumber from the standpoint ofmoisture content, evidencing less shrinkage than with kiln-dried lumber,and no weakening of the lumber occurred as a result of the treatment.Moreover, the product has excellent water-resistant properties due tothe inclusion of the wax in the treating medium. The addition of the waxis not essential insofar as drying alone is concerned, and it may beomitted if desired, but the use of the wax is greatly desirable insofaras imparting water-resistance to the lumber is concerned.

The process of this invention has been applied to many varieties oflumber, including Douglas tir, redwood, Phillipine mahogany, oak,primavera rosa morada, Brazilian pine, cedar, spruce and aspen.

Having -fully described my invention, it is to be understood that I donot wish to be limited to the details set forth, but my invention is ofthe full scope of the appended claims.

I claim:

1. A process for treating green lumber which comprises stearning thelumber and then contacting the lumber with a water-immiscible liquid ata temperature i above about 212 F. and at normal atmospheric pressurefor a suicient length of time to drive a substantial amount of waterfrom the lumber, without appreciable absorption of said water-immiscibleliquid in said lumber.

2. A process for treating green lumber which comprises steaming thelumber and then contacting the lumber with a water-immiscible liquid ata temperature between about 250 and about 450 F. and at normalatmospheric pressure for a sufficient length of time to drive asubstantial amount of water from the lumber, without appreciableabsorption of said water-immiscible liquid in said lumber.

3. A process for treating green lumber which comprises steaming thelumber and then contacting the lumber with a water-immiscible liquidcontaining about 1% by weight of a high-melting wax at a temperatureabove about 212 F. and at normal atmospheric pressure for a sucientlength of time to drive a substantial amount of water from the lumber,without appreciable absorption of said water-immiscible liquid in saidlumber.

4. A process for treating green lumber which comprises steaming thelumber and then contacting the lumber with a water-immiscible liquidcontaining about 1% by weight of a high-melting wax at a temperaturebetween about 250 F. and about 450 F. and at normal atmospheric pressurefor a suicient length of time to drive a substantial amount of waterfrom the lumber, without appreciable absorption of said water-immiscibleliquid in said lumber.

5. A process for treating green lumber which comprises steaming thelumber and then contacting the lumber with aA petroleum solvent at atemperature above about 212 F. and at a normal atmospheric pressure fora sucient length of time to drive a substantial amount of water from thelumber, without appreciable absorption of said petroleum solvent in saidlumber.

6. A process for treating green lumber which comprises steaming thelumber and then contacting the lumber with a petroleum solvent at atemperature between about 250 and about 450 F. and at normal atmosphericpressure for a sufficient length of time to drive a substantial amountof water from the lumber, without appreciable absorption of saidpetroleum solvent in said lumber.

7. A process for treating green lumber which comprises steaming thelumber and then contacting the lumber with a petroleum solventcontaining about 1% by weight of a high-melting wax at a temperatureabove about 212 F. and at normal atmospheric pressure or a suicientlength of time to drive a substantial amount of water from the lumber,without appreciable absorption of said petroleum solvent in said lumber.

8. A process for treating green lumber which comprises steaming thelumber and then contacting the lumber with a petroleum solventcontaining about 1% by weight of a high-melting wax at a temperaturebetween about 250 F. and about 450 F. and at normal atmospheric pressurefor a suflicient length of time to drive a substantial amount of waterfrom the lumber, without appreciable absorption of said petroleumsolvent in said lumber.

9. A process for treating green lumber which comprises steaming thelumber and then contacting the lumber with a petroleum solvent having aboiling range of 360- 450 F. at a temperature above about 212 F. and atnormal atmospheric pressure for a sucient length of time to drive asubstantial amount of Water from the lumber, without appreciableabsorption of said pertoleum solvent in said lumber.

l0. A process for treating green lumber which comprises steaming thelumber, contacting the lumber at a temperature above about 212 F. with apetroleum solvent having a boiling range of S60-450 F., containing 6about 1% by weight of a high-melting wax, and at normal atmosphericpressure for a suicient length of time to drive a substantial amount ofwater from the lumber, Without appreciable absorption of said petroleumsolvent in said lumber.

1l. A process for treating green lumber which comprises steaming thelumber, then contacting the lumber with a water-immiscible liquid at atemperature above about 212 F. and at normal atmospheric pressure for asuticient length of time to drive a substantial amount of water from thelumber, without appreciable absorption of said water-immiscible liquidin said lumber removing said liquid, and steaming the lumber to removeresidual vapors therefrom.

12. A process for treating .green lumber which comprises steaming thelumber, then contacting the lumber with a Water-immiscible liquid at atemperature above about 212 F. and at normal atmospheric pressure for asucient length of time to drive a substantial amount of water from thelumber, without appreciable absorption of said water-immiscible liquidin said lumber, removing said liquid, steaming the lumber and thenblowing air thereover to remove residual water vapors therefrom.

References Cited in the file of this patent UNITED STATES PATENTS686,582 Brinkerhoff Nov. 12, 1901 990,246 Fetterman Apr. 25, 19111,648,294 Coolidge Nov. 8, 1927 1,967,990 Edwards July 24, 19342,060,902 Stamm Nov. 17, 1936 2,137,404 Hollerer Nov. 22, 1938 2,507,190Barksdale May 9, 1950

